Io 

One of the four Galilean moons of Jupiter, so called because of being discovered by Galileo. The most volcanically active object in the Solar system.

Hey, look in my telescope: you can see Io, Europa, Ganymede, and Callisto.

Io by antinous February 2, 2004

IO 

Acronym for Irrelevant One

Kimmie nicknamed herself IO after falling for Ben's crap for time one hundred. I hate to agree but he sure doesn't seem to care much about her feelings.

IO by Shyantha December 22, 2006

IO 

Acronym (Slang) for "I'm Out" when conversing using the Microsoft Communicator Software. v. The act of hastily departing an online collaboration session with little notice to others participating in the dialogue.

I am no longer part of this conversation as it is digressing rapidly; it will inevitably over-step that invisible moral line in the sand that uniquely distinguishes the employed from the homeless.

<message>
"Dude, I wanna dip it in the new workstudy sittin in the corner desk..."
<reply>
"IO"
<end of converstion>

IO by Big G Funk March 17, 2009

IO 

IO

Instant Orgasm, used by girls to describe something they find attractive and or hot.

"Wow! that sports car is cool." "Yeah! its a total IO."

IO by aussieslang101 November 12, 2009

Io 

One of Jupiter's moons. It has colourful volcanic lava!!

"hey, did you know that Jupiter's moon, Io, has colourful volcanic lava?"

Io by riot ghouls rule July 29, 2021

io 

A british* acronym for instead of.

The lecture is on Tue io Thu.

OR (it may be used with dots)

I bought some bananas i.o. apples.

io by veekadikoydegskupayialiyor December 31, 2012

IO 

Shorthand for "it's Over"

Daniel: "Your Craigslist buyer backed out..."
Marianne: "IO."

IO by mabmoney June 11, 2015